The present invention concerns an autoclave, especially for articles which are used in medical treatment, with a sterilization chamber which can be locked with a door, a control unit to control and monitor various sterilization programs, with operating elements to input control signals to the control unit, as well as an indicator panel to guide the user and to display status information.
All microorganisms capable of reproduction, including their especially resistant spores, are killed through sterilization. This also applies to microorganisums which are not pathogens, but which could endanger weakened patients, e.g. through pyrogenic, i.e. febrifacient metabolic products. Viruses are inactivated irreversibly.
Thus articles used in medical treatment are sterilized when a patient's natural resistance to microorganisms is impaired. This would apply, for example, in the case of open wounds (operations following accidents, etc.), inside body cavities and mucous membranes (endoscopy), where there is unprotected layers of tissue (as a result of burns), as well as in the case of changed immunological reactions (following transplantations).
Autoclaves are made especially to sterilize articles which were previously packaged in special paper or in special plastic.
With the frequently used steam sterilization, saturated steam, which penetrates the packaging material, condenses on the articles to be sterilized. The condensation heat heats these articles up. Hot condensate penetrates the cell membranes of the microorganisms and attacks the nuclei directly. Saturated steam sterilizes very reliably despite relatively low sterilization temperature and short reaction time. Steam does not leave behind any poisonous residue on the sterilized objects.
Use of steam sterilization is preferred for textiles of cotton or heat-resistant mixed fabrics, for metal objects with sufficient corrosion resistance and for many articles of rubber, plastic, ceramic or glass. The sterilization temperature in these cases is usually 134 degrees. Cellulose, liquids, delicate rubber goods, plastic parts, also articles of glass and delicate mechanical devices are sterilized at a reduced temperature of 120 degrees.
It is important to consider the fact that the articles to be sterilized with saturated steam must remain stable when exposed to rising temperature, moisture, and the unavoidable changes in pressure and temperature. Organic materials are not suitable for sterilization in steam.
During the condensation of the saturated steam, air and other non-condensable gases are discharged on, or in, the object to be sterilized. The removal of these gases prior to sterilization and the drying of the sterilized object are the most important tasks of steam sterilization technology.
The object to be sterilized plays an important role in the sterilization process. The sterilization process depends upon the heat absorption of this object, thus upon its rise in temperature, its weight and its specific heat as well as its impedance, which prevents a free flowing off of the air. Instruments and special articles are more difficult to sterilize than textiles. Consequently various sterilization processes have proved suitable for various types or classes of objects to be sterilized which have then been incorporated into a preferably applied sterilization program for the corresponding class.
An autoclave generally comprises a sterilization chamber which can be locked with a door, the chamber, thermally insulated, being preferably of double-shell design. A blast of steam under pressure can be introduced into the sterilization chamber whereby a hot, humid climate with a certain temperature and with a certain excess pressure can build up. By means of a vacuum pump, the pressure in the sterilization chamber can likewise be reduced for certain sterilization phases. Installed in the sterilization chamber to measure the temperature and the absolute pressure are at least a thermometer and a manometer. A control unit serves to control and monitor the individual steps or sterilization phases during the course of a program. By means of operating elements, individual sterilization programs can be selected and started for particular articles to be sterilized. Important data such as the temperature and the pressure in the sterilization chamber are displayed on an indicator panel. The autoclave is usually surrounded by a casing, preferably of chrome nickel steel.
A sterilization process runs in such a way that, depending upon the object to be sterilized, a vacuum is formed at least once for at least a short time prior to the actual sterilization in which hot steam under a pressure of about 2 to 4 bar and at a temperature of 120 degrees to about 140 degrees is present in the sterilization chamber for roughly 1 to 30 minutes. A fractionated vacuum process can be applied in which, by introducing blasts of steam, following the building up of a vacuum, the vacuum disintegrates and is finally formed again. This cycle of build-up and disintegration can take place a few times, preferably about three times. In this way air bubbles present in inaccessible places on the objects to be sterilized can be reliably removed before the actual sterilization. Following sterilization another vacuum is formed in the sterilization chamber and is maintained for some minutes. This vacuum serves to dry the sterile objects. The drying process can likewise be carried out with a fractionated vacuum process.
That flawlessly sterile articles are used can be vital for patients. Operation of the autoclave thus requires the the greatest care and is not to be done by just anyone. To prevent just anyone from operating the appliance and to have perfect controls on the personnel authorized to operate it, and to make sterilization programs more flexible, improvements in autoclaves have been sought.